Microstructure Evolution in 5083 AI-Mg Alloy Exhibiting Low Temperature Superplasticity at 250°C

The current study developed a simple rolling-type TMT to process the commercial 5083 to exhibit low temperature superplasticity at 250 °C and 1×10^-3 s^-1, with an optimum tensile elongation to 400%. The TMT processed thin sheet contained (sub)grains measuring 0.5×0.5×0.2 μm. During superplastic straining, the subgrains gradually transformed into well-defined equiaxed grains to ∼1 μm at ε=0.5 and ∼1.5 μm at ε=0.9. At temperatures lower than 300 °C, the grains grew limitedly and maintained LTSP, with failure by cavitation coalescence. The flow stress of the LTSP specimens dropped to nearly one half as compared with the AR non-superplastic samples, and the strain rate sensitivity increased from 0.15-0.2 of the AR specimens to 0.3-0.4 of the LTSP ones. The effects from rolling temperature and rolling reduction ratio on the LTSP characteristics were also examined.